Aneurysms, which are abnormal dilatations of arterial walls, are abdominal aortic and thoracic aortic aneurysms. The abdominal aortic aneurysm is usually an aneurysm in the abdominal part of an artery located in the vicinity of two iliac arteries or near renal arteries. In addition, the thoracic aortic aneurysm is an aneurysm in the thoracic part of the aorta. There is the risk of rupturing an aneurysm to cause fatal massive bleeding if the aneurysm is left unattended without being treated.
A surgical bypass operation is usually performed for treatment of an abdominal aortic aneurysm. In this operation, a graft is placed in an affected part or a dilated segment. This operation, which is a treatment technique by incision by a transperitoneal or retroperitoneal procedure, the treatment technique of resecting an aneurysmal part and replacing a resected part with a synthetic graft, has been risky. Complications due to the operation include myocardial ischemia, renal failure, impotence, intestinal ischemia, infections, lower limb ischemia, spinal cord injuries with paralysis, aorta-internal organ fistulas, and the like. In the worst case, death is caused. Surgical treatment of an abdominal aortic aneurysm has a high mortality rate.
Also, the surgical treatment of an abdominal aortic aneurysm has such problems that its mortality rate is high, a recovery period is prolonged because of making a great incision of the abdomen and opening the abdominal cavity, it is difficult to suture a graft to the aorta, natural thrombotic activity which supports and strengthens the graft is lost, and emergency surgery is required when an artery is ruptured. In addition, since many patients with abdominal aortic aneurysms are elderly and therefore may have other chronic diseases such as cardiac disease, lung disease, liver disease, and (or) renal disease, it cannot be said that they are ideal for persons targeted for the operation.
When an aneurysm is generated in the thoracic aorta, reconstruction by an operation is a treatment method performed widely, like the case of the abdominal aortic aneurysm. In this operation, treatment of replacing an aneurysm segment with a prosthesis instrument is performed. However, this operation always has a high risk as described above as well as has a high mortality rate and a high morbidity rate.
On the other hand, a lot of researches on treatment methods using catheters have been conducted. The treatment methods using catheters have been facilitated by development of stent grafts. The treatment methods can shorten a period in which a patient is in a hospital and an ICU and have an advantage that a morbidity rate and a mortality rate due to an operation are low.
Generally, a surgical incision of an artery distant from an affected part, such as a common femoral or brachial artery, is made to transport a stent graft through a catheter inserted therefrom to the affected part under fluoroscopy. An introducer with an appropriate size is fitted in a guide wire, and the catheter and the guide wire are passed into an aneurysm. Then, the stent graft is advanced to an appropriate position along the guide wire through the introducer. Most stent grafts are self-expandable but may require an additional intracatheter procedure, such as balloon angioplasty, for fixing the position of a stent graft. A standard angiogram can be obtained by injecting an X-ray contrast medium into an affected part following the placement of the stent graft.
Since the above-mentioned catheter has a large diameter of typically around 20 French (Fr) (3 Fr=1 mm), it cannot be said that it is lowly invasive in the current situation, and reconstruction by a surgical operation is necessary for closure of the incised part of an artery. In addition, patients with small vessels are out of the scope of its application, since it is difficult to insert a stent graft, and have not yet retained the benefit of this treatment. Accordingly, it is necessary to design a stent graft that can be held by a catheter with a smaller diameter. Specifically, such thought as to narrow a stent and a fabric when being folded and to keep flexibility is put into the stent graft to enable its insertion into even minimum vessel when it is inserted into a vessel and/or the like.
It is conceivable that a conventional fabric is more thinned for improvement in a base fabric for a stent graft. However, when it is simply thinned, there are the problems of decreasing the strength of the fabric and increasing its permeability. Thus, disclosed is a base fabric on the surface of which microfibers are raised and which has a thickness of 0.2 mm or less in the state where the base fabric is compressed during insertion and has a thickness of 0.4 mm or more after placement into a vessel (e.g., see Patent Literature 1). Also, disclosed is the technology of making yarn constituting a woven fabric and/or the like have 5 to 40 denier to make a thin structure (see Patent Literature 2).